For a general background field \(eB\) , the spin polarization of quark
can be extracted from the quark condensate term through [1]}, [2]}, [3]}
\(\langle \bar{q}\sigma ^{12}q\rangle &=& Q_{f}\cdot eB\cdot \langle \bar{q}q\rangle \cdot \chi _{f} \approx Q_{f}\cdot eB\cdot \langle \bar{q}q\rangle \cdot \frac{\kappa _{2}P_{f}}{eB} =\kappa _{2}Q_{f}P_{f}\cdot \langle \bar{q}q\rangle .\) 
